This invention relates to air ionization apparatus, and more particularly to apparatus of specific design for improved air ion generation and cleaning.
Air ionization apparatus is commonly disposed within a work area where electrostatic surface charges are to be neutralized, such as on semiconductor wafers during fabrication of integrated circuits. Contemporary air ionization apparatus for use in large work areas commonly includes so-called ionizer bares that are formed as elongated housings having apertures spaced along the length, with ion electrodes or emitter points positioned within each aperture and connected to sources of positive or negative high voltages suitable for ionizing air about such emitter points. A source of air or relatively inert gas such as nitrogen under pressure is commonly supplied to the housing for escape therefrom through the apertures about the emitter points. In this way, generated air ions are transported away from the emitter points at which they are generated in a flowing stream of air (or gas) to be dispersed throughout the work area. For convenience and safety, generators of the high ionization voltages supplied to the emitter points are mounted within the housing and are powered by lower voltages that can be supplied to such housings with considerably lower required safety precautions. In addition, air or gas under pressure can be supplied to one or more housings through convenient tubing and pressure fittings that facilitate concatenating the installation of such ionizing bars over large work areas.
In such air ionizing apparatus, the pressured air or gas fills the entire housing and contaminant particles are known to precipitate out of the supplied stream of air or gas under pressure and accumulate over time within the housing, particularly within interior regions thereof that are out of the stream of air or gas flowing between an input to the housing and one or other of the outflow apertures. Also, containment particles may accumulate within the housing during and as a result of the various manufacturing processes involved. Thus, contaminant particles are known to collect in comers and crevices within the interior of the housing and about the circuit module inside the housing that generates the high ionizing voltages which are supplied to the emitter points. Periodic cleaning of such conventional ionizing bars is commonly achieved by dismantling the housing to expose the interior and the apertures to cleaning jets of high pressure air manually directed into comers, crevices, and about circuit modules and through the outflow apertures in order to dislodge and expel accumulated contaminant particles. Alternatively, high pressure air supplied at greater pressure and volume than under normal operation can be supplied to the housing to dislodge and expel accumulated contaminant particles, but such cleaning techniques do not reliably expel contaminant particles accumulated in corners and crevices within the housing, and therefore leave contaminant particles available to dislodge and later flow through outflow apertures into the surrounding work area.
In accordance with one embodiment of the present invention, an ionizing bar is designed for improved fluid inflow and cleaning to promote more thorough and convenient cleaning procedures, and to facilitate generation of air ions with reduced prospects for particulate contaminants being emitted with generated air ions. These benefits are achieved using fluid flow conduits connected between and among the outflow apertures and an inlet to confine operational airflow within fluid flow conduits, and thereby to isolate the supplied air under pressure from the housing surfaces and high-voltage circuit module in the interior of the housing. Tubing connections from the inlet to each aperture assure minimal surface area contacted by air or gas supplied under pressure, and isolates the high-voltage circuit module from contacting any fluid flow out through the apertures. Thus, more rigorous and convenient cleaning procedures can be employed, including passing liquid solvent through confining fluid conduits from the inlet to the apertures for substantially more thorough cleaning, thereby to assure thorough flushing from the system contaminant particles of even smaller sizes (i.e., less than about 2 microns) than can be flushed using conventional jets of pressurized air.